Definitely not worth 4 1/2 hours. The JFM stuff works great if you only have a little gray to cover, but there is not enough in the kit for a full beard with a lot of gray. I use another brand of hair color that is less expensive and has four times the quantity in the box (it's marketed to ladies, but the same chemicals). It take me about 20 minutes once a week and I have never had any skin reactions. They all stain the skin, so with any product you have to be careful to not get it on the surrounding skin, or wash it off immediately if you do. A skin stain will last about 24 to 48 hours.